DBI202Xuất hiện trong 2 đề thi
Assume that there is a table: And functional dependencies $\{ID \to NAME, ID \to Age, TAX\_NUMBER \to NAME, AGE, ID \to TAX\_NUMBER\}$. You are required to specify keys: primary key and unique key for the table “Employee”. Choose the most appropriate option for the table.
Các lựa chọn
AThe primary key is the ID column, the unique key is the TAX_NUMBER column
BThe primary key is the TAX_NUMBER column, the unique key is the ID column
CThe primary key includes two columns (ID, TAX_NUMBER) and there should not be a unique key.
DThe primary key is the TAX_NUMBER column, and there should not be a unique key.